The present invention relates to a method for the preparation of highly heat-resistant relief structures with a polymer base of heterocyclic structure by applying radiation-sensitive soluble polymer precursor stages in the form of a film or a foil to a substrate, irradiating the film or foil through negative patterns with actinic light or by deflecting a light, electron or ion beam, removing the non-irradiated film or foil portions and, optionally, subsequently annealing, as well as to the use of relief structures prepared in this manner.
A method for the preparation of relief structures of the type mentioned is known from German Pat. No. 2 308 830 and its corresponding U.S. Pat. No. 3,957,512. In this method, polyaddition and polycondensation products of polyfunctional carbocyclic or heterocyclic compounds carrying radiation-sensitive radicals with diamines, diisocyanates, bis-acid chlorides or dicarboxylic acids are used as soluble polymer precursor stages. The compounds which carry radiation-sensitive radicals contain two carboxyl, carboxylic-acid chloride, amino, isocyanate or hydroxyl groups suitable for addition or condensation reactions and in part, in ortho- or peri-position thereto, radiation-reactive groups which are bound to carboxyl groups in ester-fashion. The diamines, diisocyanates, bis-acid chlorides and dicarboxylic acids to be reacted with these compounds exhibit at least one cyclic structure element.
The soluble polymer precursor stages are cross-linked when irradiated and change in the process into insoluble intermediate products. In annealing, these intermediate products are subjected to cyclization, highly heat-resistant polymers of the following classes of substances being formed: Polyimides (including polyamidimides and polyesterimides), poly-1,3-quinazoline-2,6-diones, polyisoindoloquinazoline diones, poly-1,3-oxazine-6-ones and polybenz-1,3-oxazine-2,4-diones.
The relief structures prepared by the known method have found good acceptance in practice. However, it also has been found that difficulties still occur which stem from the polymer precursor stages. These precursor stages are soluble only in organic solvents, so that on the one hand, they can be processed only in such solvents, and on the other hand, the structures prepared from the polymer precursor stages by irradiation can be developed only with the aid of organic solvents. If organic developers are used for removing non-irradiated portions, however, problems with respect to toxicity and flammability, as well as problems in disposal, arise.